hi there.. owned my bug sti now for around 5 months now.. spent in the region of around 2 to 3 k on getting her pristine.. i.e carbon bonnet full service., i.c.e, etc. wont go into to much detail.. i love it. was a bit nervous at first with some of the stories u here especially wen owning a 58 plate astra vxr before hand.. everything seems to be fine apart from now and again wen i start her up she seems to misfire... all the sparks have been done and i have uprated the fuel pump also... its annoying me because this is the only fault on her... all work has been carried out by powerstation in tewkes... they have put the diags on her but cannot find any faults.. has this happened to anyone elses bug. want it sorted asap... plans for this car like u wouldnt imagine.... would it be the uprated fuel pump? cheers rob

 

Dont think the pump would cause it.

They do have a problem with the fuel line leaking under the inlet manifold, if its leaking it might be enough to cause your missfire.

Start the car up and open the bonnet and see if you can smell fuel, or ask the previous owner if he had the pipes changed..

 

Coil packs? Plugs? Plug leads?

Lots of misfires are electrical.

 

If Powerstation can't pin this down, we're going to have little chance, other than someone making a very lucky guess.

As f4 has already said, it is difficult to imagine a circumstance where the uprated fuel pump would cause a symptom like this, given that, at startup, there shouldn't, in practice, be any difference in fuel supply between the standard configuration and what you now have.

One of the things that makes it difficult to help you is that we obviously aren't aware of the exact nature of the "misfire". Are we talking about a fraction of a second's miss as the engine first catches? If so, does it happen every time you start or only occasionally? Does it misbehave at all once started and running?

Is it a Type UK or JDM car, and is it running its standard mapping or not? Information like this would help us to help you.

 

It's usually the cremated exhaust valves that will do this...

LOL

dunx

 

its a type uk with no map... it does it occasionlally wen cold and sometimes wen hot. at first start up there is a very rich fuel smell. wen shes started it sort of goes over and over and then the engine kicks in very stutterley. once shes started it runs fine no misfire as smooth as silk which u would expect as shes only done 30000 miles... wen i took it to powerstation the car was warm and hardly does it wen warm and starts up perfect wen warm 99 percent of the time... strange... any info still much appreciated... rob

 

You should expect a certain element of fuel smell when it's cold as the cold start/cold run enrichments will be switched on.

As it sounds very intermittent it's going to be difficult to pin down - and there are any number of potential explanations. Clearly if it's worse when cold the best chance anyone would have of diagnosing it is to leave it with overnight so they can actually cold start it with the relevant monitoring kit plugged in.

If it stutters for a number of seconds it should be possible to capture the cause - or to eliminate enough potential causes that there aren't too many left to deal with via a process of elimination.

However, bottom line is that if PS believe it to be running perfectly nominally under normal running conditions, it would be worth asking yourself whether the options to take would be to live with it until/unless it appears to be getting worse.

 

When were plugs last changed and what ones are fitted ?

 

Just a thought, could these have been occasions when you started the car with your foot on the accelerator...it has been known to cause similar issues